A variety of microelectronic, microtechnique, microoptic or combined devices are based on substrates which are processed in an appropriate manner. For example, substrates may be processed for forming layers of a display, photovoltaic layers, light emitting layers, or for modifying surfaces etc. In many cases, substrates are coated by thin films which can be structured during a deposition process. Thereby, typically a portion of a substrate such as an area along the circumference of a substrate or other portions of the substrates are shielded to avoid deposition of these portions. Such kinds of shielding or patterning are based on a mask arranged at a surface of a substrate to be processed. Shielding of portions of a substrate commonly results in deposition of material on a mask, which can in turn shadow the area on the substrate to be processed. Such deposition of material on a mask can reduce the uptime of a processing system.
Further, masking a substrate may be performed by using a mask foil attached to a mask frame. As integrated circuits and other structures are rapidly shrinking in feature size, micro-patterning techniques may be applied to achieve a desired minimum line width of the pattern. Patterns may be formed closely adjacent to each other on a substrate to be processed. An increasing level of complexity of device and integration of devices formed by micro-technological methods may be achieved by a processing technology based on a fine pattern of a mask device. This pattern is typically formed with a high accuracy which increases the cost of the mask device. During patterning of the substrate to be processed, the mask is arranged between a deposition source providing the deposition material and the substrate. The mask foil may include a desired pattern which is transferred, during a deposition process, onto the substrate surface. When the deposition source emits deposition material towards the surface of the substrate, the pattern of the mask foil at least partially shields the surface of the substrate to be processed from deposition material. Thus, a desired pattern may be obtained at the surface of the substrate. The same applies if a margin of the substrate is masked.
In order to obtain an efficient coverage of the substrate surface to be processed by deposition material, shadowing effects of the mask frame holding the mask foil should be avoided. Accordingly, it is desirable to reduce or control shadowing effects in order to increase uptime. In particular the shadowing effect should be reduced or controlled in such a manner that a cleaning of masks and covers should correspond to other maintenance cycles of the processing system.